DTC B2789 Id Code Box Communication: Trouble Symptom
WARNING: This page is about a different car, the 2016 Subaru Outback and 2016 Subaru Legacy. However, it is still accessible from the selected car via links, so may be relevant.
Engine will not start.
CAUTION:
For replacement procedure of keyless access control module and ID code box, refer to the "REGISTRATION MANUAL FOR IMMOBILIZER" provided as a separate volume.